Benchmarking the quantum processing power of large-scale quantum processors to execute specific programs

We propose an experimentally measurable quantity, the circuit quality Q of any hardware implementation of a quantum circuit, which can be efficiently estimated via clock cycle benchmarking, and discuss how this quantity can be applied to two key applications of circuit benchmarking: (i) determining the size of a quantum program that can be run on specific quantum hardware to within a specified tolerance; and (ii) establishing a family of cross-platform benchmarks for overall hardware performance. The first application provides an efficient means of assessing the overall error probability with which hardware can implement a quantum program beyond the horizon of classical computability, which will be tremendously important once quantum processors can outperform their classical counterparts. The second application is to define a practical, even-handed, and robust cross-platform benchmark of hardware performance for standardized quantum circuits. Our proposal for circuit benchmarking overcomes several problematic limitations of the `quantum volume’ figure of merit and the implicit recipe for measuring it. These circuit quality benchmarks will be essential to assessing and improving hardware performance on the road to practiucal quantum computation that can solve real-world problems.